drivers/md/dm-mpath.c

   1 /*
   2  * Copyright (C) 2003 Sistina Software Limited.
   3  * Copyright (C) 2004-2005 Red Hat, Inc. All rights reserved.
   4  *
   5  * This file is released under the GPL.
   6  */
   7
   8 #include <linux/device-mapper.h>
   9
  10 #include "dm-path-selector.h"
  11 #include "dm-uevent.h"
  12
  13 #include <linux/ctype.h>
  14 #include <linux/init.h>
  15 #include <linux/mempool.h>
  16 #include <linux/module.h>
  17 #include <linux/pagemap.h>
  18 #include <linux/slab.h>
  19 #include <linux/time.h>
  20 #include <linux/workqueue.h>
  21 #include <scsi/scsi_dh.h>
  22 #include <scsi/scsi_eh.h>
  23 #include <asm/atomic.h>
  24
  25 #define DM_MSG_PREFIX "multipath"
  26 #define MESG_STR(x) x, sizeof(x)
  27
  28 /* Path properties */
  29 struct pgpath {
  30         struct list_head list;
  31
  32         struct priority_group *pg;      /* Owning PG */
  33         unsigned is_active;             /* Path status */
  34         unsigned fail_count;            /* Cumulative failure count */
  35
  36         struct dm_path path;
  37         struct work_struct deactivate_path;
  38         struct work_struct activate_path;
  39 };
  40
  41 #define path_to_pgpath(__pgp) container_of((__pgp), struct pgpath, path)
  42
  43 /*
  44  * Paths are grouped into Priority Groups and numbered from 1 upwards.
  45  * Each has a path selector which controls which path gets used.
  46  */
  47 struct priority_group {
  48         struct list_head list;
  49
  50         struct multipath *m;            /* Owning multipath instance */
  51         struct path_selector ps;
  52
  53         unsigned pg_num;                /* Reference number */
  54         unsigned bypassed;              /* Temporarily bypass this PG? */
  55
  56         unsigned nr_pgpaths;            /* Number of paths in PG */
  57         struct list_head pgpaths;
  58 };
  59
  60 #define FEATURE_NO_PARTITIONS 1
  61
  62 /* Multipath context */
  63 struct multipath {
  64         struct list_head list;
  65         struct dm_target *ti;
  66
  67         spinlock_t lock;
  68
  69         const char *hw_handler_name;
  70         char *hw_handler_params;
  71         unsigned nr_priority_groups;
  72         struct list_head priority_groups;
  73         unsigned pg_init_required;      /* pg_init needs calling? */
  74         unsigned pg_init_in_progress;   /* Only one pg_init allowed at once */
  75         wait_queue_head_t pg_init_wait; /* Wait for pg_init completion */
  76
  77         unsigned nr_valid_paths;        /* Total number of usable paths */
  78         struct pgpath *current_pgpath;
  79         struct priority_group *current_pg;
  80         struct priority_group *next_pg; /* Switch to this PG if set */
  81         unsigned repeat_count;          /* I/Os left before calling PS again */
  82
  83         unsigned queue_io;              /* Must we queue all I/O? */
  84         unsigned queue_if_no_path;      /* Queue I/O if last path fails? */
  85         unsigned saved_queue_if_no_path;/* Saved state during suspension */
  86         unsigned pg_init_retries;       /* Number of times to retry pg_init */
  87         unsigned pg_init_count;         /* Number of times pg_init called */
  88         unsigned features;              /* Additional selected features */
  89
  90         struct work_struct process_queued_ios;
  91         struct list_head queued_ios;
  92         unsigned queue_size;
  93
  94         struct work_struct trigger_event;
  95
  96         /*
  97          * We must use a mempool of dm_mpath_io structs so that we
  98          * can resubmit bios on error.
  99          */
 100         mempool_t *mpio_pool;
 101
 102         struct mutex work_mutex;
 103 };
 104
 105 /*
 106  * Context information attached to each bio we process.
 107  */
 108 struct dm_mpath_io {
 109         struct pgpath *pgpath;
 110         size_t nr_bytes;
 111         char sense[SCSI_SENSE_BUFFERSIZE];
 112 };
 113
 114 typedef int (*action_fn) (struct pgpath *pgpath);
 115
 116 #define MIN_IOS 256     /* Mempool size */
 117
 118 static struct kmem_cache *_mpio_cache;
 119
 120 static struct workqueue_struct *kmultipathd, *kmpath_handlerd;
 121 static void process_queued_ios(struct work_struct *work);
 122 static void trigger_event(struct work_struct *work);
 123 static void activate_path(struct work_struct *work);
 124 static void deactivate_path(struct work_struct *work);
 125
 126
 127 /*-----------------------------------------------
 128  * Allocation routines
 129  *-----------------------------------------------*/
 130
 131 static struct pgpath *alloc_pgpath(void)
 132 {
 133         struct pgpath *pgpath = kzalloc(sizeof(*pgpath), GFP_KERNEL);
 134
 135         if (pgpath) {
 136                 pgpath->is_active = 1;
 137                 INIT_WORK(&pgpath->deactivate_path, deactivate_path);
 138                 INIT_WORK(&pgpath->activate_path, activate_path);
 139         }
 140
 141         return pgpath;
 142 }
 143
 144 static void free_pgpath(struct pgpath *pgpath)
 145 {
 146         kfree(pgpath);
 147 }
 148
 149 static void deactivate_path(struct work_struct *work)
 150 {
 151         struct pgpath *pgpath =
 152                 container_of(work, struct pgpath, deactivate_path);
 153
 154         if (pgpath->path.dev)
 155                 blk_abort_queue(pgpath->path.dev->bdev->bd_disk->queue);
 156 }
 157
 158 static struct priority_group *alloc_priority_group(void)
 159 {
 160         struct priority_group *pg;
 161
 162         pg = kzalloc(sizeof(*pg), GFP_KERNEL);
 163
 164         if (pg)
 165                 INIT_LIST_HEAD(&pg->pgpaths);
 166
 167         return pg;
 168 }
 169
 170 static void free_pgpaths(struct list_head *pgpaths, struct dm_target *ti)
 171 {
 172         struct pgpath *pgpath, *tmp;
 173         struct multipath *m = ti->private;
 174
 175         list_for_each_entry_safe(pgpath, tmp, pgpaths, list) {
 176                 list_del(&pgpath->list);
 177                 dm_put_device(ti, pgpath->path.dev);
 178                 free_pgpath(pgpath);
 179         }
 180 }
 181
 182 static void free_priority_group(struct priority_group *pg,
 183                                 struct dm_target *ti)
 184 {
 185         struct path_selector *ps = &pg->ps;
 186
 187         if (ps->type) {
 188                 ps->type->destroy(ps);
 189                 dm_put_path_selector(ps->type);
 190         }
 191
 192         free_pgpaths(&pg->pgpaths, ti);
 193         kfree(pg);
 194 }
 195
 196 static struct multipath *alloc_multipath(struct dm_target *ti)
 197 {
 198         struct multipath *m;
 199
 200         m = kzalloc(sizeof(*m), GFP_KERNEL);
 201         if (m) {
 202                 INIT_LIST_HEAD(&m->priority_groups);
 203                 INIT_LIST_HEAD(&m->queued_ios);
 204                 spin_lock_init(&m->lock);
 205                 m->queue_io = 1;
 206                 INIT_WORK(&m->process_queued_ios, process_queued_ios);
 207                 INIT_WORK(&m->trigger_event, trigger_event);
 208                 init_waitqueue_head(&m->pg_init_wait);
 209                 mutex_init(&m->work_mutex);
 210                 m->mpio_pool = mempool_create_slab_pool(MIN_IOS, _mpio_cache);
 211                 if (!m->mpio_pool) {
 212                         kfree(m);
 213                         return NULL;
 214                 }
 215                 m->ti = ti;
 216                 ti->private = m;
 217         }
 218
 219         return m;
 220 }
 221
 222 static void free_multipath(struct multipath *m)
 223 {
 224         struct priority_group *pg, *tmp;
 225
 226         list_for_each_entry_safe(pg, tmp, &m->priority_groups, list) {
 227                 list_del(&pg->list);
 228                 free_priority_group(pg, m->ti);
 229         }
 230
 231         kfree(m->hw_handler_name);
 232         kfree(m->hw_handler_params);
 233         mempool_destroy(m->mpio_pool);
 234         kfree(m);
 235 }
 236
 237
 238 /*-----------------------------------------------
 239  * Path selection
 240  *-----------------------------------------------*/
 241
 242 static void __pg_init_all_paths(struct multipath *m)
 243 {
 244         struct pgpath *pgpath;
 245
 246         m->pg_init_count++;
 247         m->pg_init_required = 0;
 248         list_for_each_entry(pgpath, &m->current_pg->pgpaths, list) {
 249                 /* Skip failed paths */
 250                 if (!pgpath->is_active)
 251                         continue;
 252                 if (queue_work(kmpath_handlerd, &pgpath->activate_path))
 253                         m->pg_init_in_progress++;
 254         }
 255 }
 256
 257 static void __switch_pg(struct multipath *m, struct pgpath *pgpath)
 258 {
 259         m->current_pg = pgpath->pg;
 260
 261         /* Must we initialise the PG first, and queue I/O till it's ready? */
 262         if (m->hw_handler_name) {
 263                 m->pg_init_required = 1;
 264                 m->queue_io = 1;
 265         } else {
 266                 m->pg_init_required = 0;
 267                 m->queue_io = 0;
 268         }
 269
 270         m->pg_init_count = 0;
 271 }
 272
 273 static int __choose_path_in_pg(struct multipath *m, struct priority_group *pg,
 274                                size_t nr_bytes)
 275 {
 276         struct dm_path *path;
 277
 278         path = pg->ps.type->select_path(&pg->ps, &m->repeat_count, nr_bytes);
 279         if (!path)
 280                 return -ENXIO;
 281
 282         m->current_pgpath = path_to_pgpath(path);
 283
 284         if (!m->current_pgpath->path.dev) {
 285                 m->current_pgpath = NULL;
 286                 return -ENODEV;
 287         }
 288
 289         if (m->current_pg != pg)
 290                 __switch_pg(m, m->current_pgpath);
 291
 292         return 0;
 293 }
 294
 295 static void __choose_pgpath(struct multipath *m, size_t nr_bytes)
 296 {
 297         struct priority_group *pg;
 298         unsigned bypassed = 1;
 299
 300         if (!m->nr_valid_paths)
 301                 goto failed;
 302
 303         /* Were we instructed to switch PG? */
 304         if (m->next_pg) {
 305                 pg = m->next_pg;
 306                 m->next_pg = NULL;
 307                 if (!__choose_path_in_pg(m, pg, nr_bytes))
 308                         return;
 309         }
 310
 311         /* Don't change PG until it has no remaining paths */
 312         if (m->current_pg && !__choose_path_in_pg(m, m->current_pg, nr_bytes))
 313                 return;
 314
 315         /*
 316          * Loop through priority groups until we find a valid path.
 317          * First time we skip PGs marked 'bypassed'.
 318          * Second time we only try the ones we skipped.
 319          */
 320         do {
 321                 list_for_each_entry(pg, &m->priority_groups, list) {
 322                         if (pg->bypassed == bypassed)
 323                                 continue;
 324                         if (!__choose_path_in_pg(m, pg, nr_bytes))
 325                                 return;
 326                 }
 327         } while (bypassed--);
 328
 329 failed:
 330         m->current_pgpath = NULL;
 331         m->current_pg = NULL;
 332 }
 333
 334 /*
 335  * Check whether bios must be queued in the device-mapper core rather
 336  * than here in the target.
 337  *
 338  * m->lock must be held on entry.
 339  *
 340  * If m->queue_if_no_path and m->saved_queue_if_no_path hold the
 341  * same value then we are not between multipath_presuspend()
 342  * and multipath_resume() calls and we have no need to check
 343  * for the DMF_NOFLUSH_SUSPENDING flag.
 344  */
 345 static int __must_push_back(struct multipath *m)
 346 {
 347         return (m->queue_if_no_path != m->saved_queue_if_no_path &&
 348                 dm_noflush_suspending(m->ti));
 349 }
 350
 351 static int map_io(struct multipath *m, struct request *clone,
 352                   struct dm_mpath_io *mpio, unsigned was_queued)
 353 {
 354         int r = DM_MAPIO_REMAPPED;
 355         size_t nr_bytes = blk_rq_bytes(clone);
 356         unsigned long flags;
 357         struct pgpath *pgpath;
 358         struct block_device *bdev;
 359
 360         spin_lock_irqsave(&m->lock, flags);
 361
 362         /* Do we need to select a new pgpath? */
 363         if (!m->current_pgpath ||
 364             (!m->queue_io && (m->repeat_count && --m->repeat_count == 0)))
 365                 __choose_pgpath(m, nr_bytes);
 366
 367         pgpath = m->current_pgpath;
 368
 369         if (was_queued)
 370                 m->queue_size--;
 371
 372         if ((pgpath && m->queue_io) ||
 373             (!pgpath && m->queue_if_no_path)) {
 374                 /* Queue for the daemon to resubmit */
 375                 list_add_tail(&clone->queuelist, &m->queued_ios);
 376                 m->queue_size++;
 377                 if ((m->pg_init_required && !m->pg_init_in_progress) ||
 378                     !m->queue_io)
 379                         queue_work(kmultipathd, &m->process_queued_ios);
 380                 pgpath = NULL;
 381                 r = DM_MAPIO_SUBMITTED;
 382         } else if (pgpath) {
 383                 bdev = pgpath->path.dev->bdev;
 384                 clone->q = bdev_get_queue(bdev);
 385                 clone->rq_disk = bdev->bd_disk;
 386         } else if (__must_push_back(m))
 387                 r = DM_MAPIO_REQUEUE;
 388         else
 389                 r = -EIO;       /* Failed */
 390
 391         mpio->pgpath = pgpath;
 392         mpio->nr_bytes = nr_bytes;
 393
 394         if (r == DM_MAPIO_REMAPPED && pgpath->pg->ps.type->start_io)
 395                 pgpath->pg->ps.type->start_io(&pgpath->pg->ps, &pgpath->path,
 396                                               nr_bytes);
 397
 398         spin_unlock_irqrestore(&m->lock, flags);
 399
 400         return r;
 401 }
 402
 403 /*
 404  * If we run out of usable paths, should we queue I/O or error it?
 405  */
 406 static int queue_if_no_path(struct multipath *m, unsigned queue_if_no_path,
 407                             unsigned save_old_value)
 408 {
 409         unsigned long flags;
 410
 411         spin_lock_irqsave(&m->lock, flags);
 412
 413         if (save_old_value)
 414                 m->saved_queue_if_no_path = m->queue_if_no_path;
 415         else
 416                 m->saved_queue_if_no_path = queue_if_no_path;
 417         m->queue_if_no_path = queue_if_no_path;
 418         if (!m->queue_if_no_path && m->queue_size)
 419                 queue_work(kmultipathd, &m->process_queued_ios);
 420
 421         spin_unlock_irqrestore(&m->lock, flags);
 422
 423         return 0;
 424 }
 425
 426 /*-----------------------------------------------------------------
 427  * The multipath daemon is responsible for resubmitting queued ios.
 428  *---------------------------------------------------------------*/
 429
 430 static void dispatch_queued_ios(struct multipath *m)
 431 {
 432         int r;
 433         unsigned long flags;
 434         struct dm_mpath_io *mpio;
 435         union map_info *info;
 436         struct request *clone, *n;
 437         LIST_HEAD(cl);
 438
 439         spin_lock_irqsave(&m->lock, flags);
 440         list_splice_init(&m->queued_ios, &cl);
 441         spin_unlock_irqrestore(&m->lock, flags);
 442
 443         list_for_each_entry_safe(clone, n, &cl, queuelist) {
 444                 list_del_init(&clone->queuelist);
 445
 446                 info = dm_get_rq_mapinfo(clone);
 447                 mpio = info->ptr;
 448
 449                 r = map_io(m, clone, mpio, 1);
 450                 if (r < 0) {
 451                         mempool_free(mpio, m->mpio_pool);
 452                         dm_kill_unmapped_request(clone, r);
 453                 } else if (r == DM_MAPIO_REMAPPED)
 454                         dm_dispatch_request(clone);
 455                 else if (r == DM_MAPIO_REQUEUE) {
 456                         mempool_free(mpio, m->mpio_pool);
 457                         dm_requeue_unmapped_request(clone);
 458                 }
 459         }
 460 }
 461
 462 static void process_queued_ios(struct work_struct *work)
 463 {
 464         struct multipath *m =
 465                 container_of(work, struct multipath, process_queued_ios);
 466         struct pgpath *pgpath = NULL;
 467         unsigned must_queue = 1;
 468         unsigned long flags;
 469
 470         spin_lock_irqsave(&m->lock, flags);
 471
 472         if (!m->queue_size)
 473                 goto out;
 474
 475         if (!m->current_pgpath)
 476                 __choose_pgpath(m, 0);
 477
 478         pgpath = m->current_pgpath;
 479
 480         if ((pgpath && !m->queue_io) ||
 481             (!pgpath && !m->queue_if_no_path))
 482                 must_queue = 0;
 483
 484         if (m->pg_init_required && !m->pg_init_in_progress && pgpath)
 485                 __pg_init_all_paths(m);
 486
 487 out:
 488         spin_unlock_irqrestore(&m->lock, flags);
 489         if (!must_queue)
 490                 dispatch_queued_ios(m);
 491 }
 492
 493 /*
 494  * An event is triggered whenever a path is taken out of use.
 495  * Includes path failure and PG bypass.
 496  */
 497 static void trigger_event(struct work_struct *work)
 498 {
 499         struct multipath *m =
 500                 container_of(work, struct multipath, trigger_event);
 501
 502         dm_table_event(m->ti->table);
 503 }
 504
 505 /*-----------------------------------------------------------------
 506  * Constructor/argument parsing:
 507  * <#multipath feature args> [<arg>]*
 508  * <#hw_handler args> [hw_handler [<arg>]*]
 509  * <#priority groups>
 510  * <initial priority group>
 511  *     [<selector> <#selector args> [<arg>]*
 512  *      <#paths> <#per-path selector args>
 513  *         [<path> [<arg>]* ]+ ]+
 514  *---------------------------------------------------------------*/
 515 struct param {
 516         unsigned min;
 517         unsigned max;
 518         char *error;
 519 };
 520
 521 static int read_param(struct param *param, char *str, unsigned *v, char **error)
 522 {
 523         if (!str ||
 524             (sscanf(str, "%u", v) != 1) ||
 525             (*v < param->min) ||
 526             (*v > param->max)) {
 527                 *error = param->error;
 528                 return -EINVAL;
 529         }
 530
 531         return 0;
 532 }
 533
 534 struct arg_set {
 535         unsigned argc;
 536         char **argv;
 537 };
 538
 539 static char *shift(struct arg_set *as)
 540 {
 541         char *r;
 542
 543         if (as->argc) {
 544                 as->argc--;
 545                 r = *as->argv;
 546                 as->argv++;
 547                 return r;
 548         }
 549
 550         return NULL;
 551 }
 552
 553 static void consume(struct arg_set *as, unsigned n)
 554 {
 555         BUG_ON (as->argc < n);
 556         as->argc -= n;
 557         as->argv += n;
 558 }
 559
 560 static int parse_path_selector(struct arg_set *as, struct priority_group *pg,
 561                                struct dm_target *ti)
 562 {
 563         int r;
 564         struct path_selector_type *pst;
 565         unsigned ps_argc;
 566
 567         static struct param _params[] = {
 568                 {0, 1024, "invalid number of path selector args"},
 569         };
 570
 571         pst = dm_get_path_selector(shift(as));
 572         if (!pst) {
 573                 ti->error = "unknown path selector type";
 574                 return -EINVAL;
 575         }
 576
 577         r = read_param(_params, shift(as), &ps_argc, &ti->error);
 578         if (r) {
 579                 dm_put_path_selector(pst);
 580                 return -EINVAL;
 581         }
 582
 583         if (ps_argc > as->argc) {
 584                 dm_put_path_selector(pst);
 585                 ti->error = "not enough arguments for path selector";
 586                 return -EINVAL;
 587         }
 588
 589         r = pst->create(&pg->ps, ps_argc, as->argv);
 590         if (r) {
 591                 dm_put_path_selector(pst);
 592                 ti->error = "path selector constructor failed";
 593                 return r;
 594         }
 595
 596         pg->ps.type = pst;
 597         consume(as, ps_argc);
 598
 599         return 0;
 600 }
 601
 602 static struct pgpath *parse_path(struct arg_set *as, struct path_selector *ps,
 603                                struct dm_target *ti)
 604 {
 605         int r;
 606         struct pgpath *p;
 607         char *path;
 608         struct multipath *m = ti->private;
 609
 610         /* we need at least a path arg */
 611         if (as->argc < 1) {
 612                 ti->error = "no device given";
 613                 return ERR_PTR(-EINVAL);
 614         }
 615
 616         p = alloc_pgpath();
 617         if (!p)
 618                 return ERR_PTR(-ENOMEM);
 619
 620         path = shift(as);
 621         r = dm_get_device(ti, path, dm_table_get_mode(ti->table),
 622                           &p->path.dev);
 623         if (r) {
 624                 unsigned major, minor;
 625
 626                 /* Try to add a failed device */
 627                 if (r == -ENXIO && sscanf(path, "%u:%u", &major, &minor) == 2) {
 628                         dev_t dev;
 629
 630                         /* Extract the major/minor numbers */
 631                         dev = MKDEV(major, minor);
 632                         if (MAJOR(dev) != major || MINOR(dev) != minor) {
 633                                 /* Nice try, didn't work */
 634                                 DMWARN("Invalid device path %s", path);
 635                                 ti->error = "error converting devnum";
 636                                 goto bad;
 637                         }
 638                         DMWARN("adding disabled device %d:%d", major, minor);
 639                         p->path.dev = NULL;
 640                         format_dev_t(p->path.pdev, dev);
 641                         p->is_active = 0;
 642                 } else {
 643                         ti->error = "error getting device";
 644                         goto bad;
 645                 }
 646         } else {
 647                 memcpy(p->path.pdev, p->path.dev->name, 16);
 648         }
 649
 650         if (p->path.dev) {
 651                 struct request_queue *q = bdev_get_queue(p->path.dev->bdev);
 652
 653                 if (m->hw_handler_name) {
 654                         r = scsi_dh_attach(q, m->hw_handler_name);
 655                         if (r == -EBUSY) {
 656                                 /*
 657                                  * Already attached to different hw_handler,
 658                                  * try to reattach with correct one.
 659                                  */
 660                                 scsi_dh_detach(q);
 661                                 r = scsi_dh_attach(q, m->hw_handler_name);
 662                         }
 663                         if (r < 0) {
 664                                 ti->error = "error attaching hardware handler";
 665                                 dm_put_device(ti, p->path.dev);
 666                                 goto bad;
 667                         }
 668                 } else {
 669                         /* Play safe and detach hardware handler */
 670                         scsi_dh_detach(q);
 671                 }
 672
 673                 if (m->hw_handler_params) {
 674                         r = scsi_dh_set_params(q, m->hw_handler_params);
 675                         if (r < 0) {
 676                                 ti->error = "unable to set hardware "
 677                                                         "handler parameters";
 678                                 scsi_dh_detach(q);
 679                                 dm_put_device(ti, p->path.dev);
 680                                 goto bad;
 681                         }
 682                 }
 683         }
 684
 685         r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
 686         if (r) {
 687                 dm_put_device(ti, p->path.dev);
 688                 goto bad;
 689         }
 690
 691         if (!p->is_active) {
 692                 ps->type->fail_path(ps, &p->path);
 693                 p->fail_count++;
 694                 m->nr_valid_paths--;
 695         }
 696         return p;
 697
 698  bad:
 699         free_pgpath(p);
 700         return ERR_PTR(r);
 701 }
 702
 703 static struct priority_group *parse_priority_group(struct arg_set *as,
 704                                                    struct multipath *m)
 705 {
 706         static struct param _params[] = {
 707                 {1, 1024, "invalid number of paths"},
 708                 {0, 1024, "invalid number of selector args"}
 709         };
 710
 711         int r;
 712         unsigned i, nr_selector_args, nr_params;
 713         struct priority_group *pg;
 714         struct dm_target *ti = m->ti;
 715
 716         if (as->argc < 2) {
 717                 as->argc = 0;
 718                 ti->error = "not enough priority group arguments";
 719                 return ERR_PTR(-EINVAL);
 720         }
 721
 722         pg = alloc_priority_group();
 723         if (!pg) {
 724                 ti->error = "couldn't allocate priority group";
 725                 return ERR_PTR(-ENOMEM);
 726         }
 727         pg->m = m;
 728
 729         r = parse_path_selector(as, pg, ti);
 730         if (r)
 731                 goto bad;
 732
 733         /*
 734          * read the paths
 735          */
 736         r = read_param(_params, shift(as), &pg->nr_pgpaths, &ti->error);
 737         if (r)
 738                 goto bad;
 739
 740         r = read_param(_params + 1, shift(as), &nr_selector_args, &ti->error);
 741         if (r)
 742                 goto bad;
 743
 744         nr_params = 1 + nr_selector_args;
 745         for (i = 0; i < pg->nr_pgpaths; i++) {
 746                 struct pgpath *pgpath;
 747                 struct arg_set path_args;
 748
 749                 if (as->argc < nr_params) {
 750                         ti->error = "not enough path parameters";
 751                         goto bad;
 752                 }
 753
 754                 path_args.argc = nr_params;
 755                 path_args.argv = as->argv;
 756
 757                 pgpath = parse_path(&path_args, &pg->ps, ti);
 758                 if (IS_ERR(pgpath)) {
 759                         r = PTR_ERR(pgpath);
 760                         goto bad;
 761                 }
 762
 763                 pgpath->pg = pg;
 764                 list_add_tail(&pgpath->list, &pg->pgpaths);
 765                 consume(as, nr_params);
 766         }
 767
 768         return pg;
 769
 770  bad:
 771         free_priority_group(pg, ti);
 772         return ERR_PTR(r);
 773 }
 774
 775 static int parse_hw_handler(struct arg_set *as, struct multipath *m)
 776 {
 777         unsigned hw_argc;
 778         int ret;
 779         struct dm_target *ti = m->ti;
 780
 781         static struct param _params[] = {
 782                 {0, 1024, "invalid number of hardware handler args"},
 783         };
 784
 785         if (read_param(_params, shift(as), &hw_argc, &ti->error))
 786                 return -EINVAL;
 787
 788         if (!hw_argc)
 789                 return 0;
 790
 791         if (hw_argc > as->argc) {
 792                 ti->error = "not enough arguments for hardware handler";
 793                 return -EINVAL;
 794         }
 795
 796         m->hw_handler_name = kstrdup(shift(as), GFP_KERNEL);
 797         request_module("scsi_dh_%s", m->hw_handler_name);
 798         if (scsi_dh_handler_exist(m->hw_handler_name) == 0) {
 799                 ti->error = "unknown hardware handler type";
 800                 ret = -EINVAL;
 801                 goto fail;
 802         }
 803
 804         if (hw_argc > 1) {
 805                 char *p;
 806                 int i, j, len = 4;
 807
 808                 for (i = 0; i <= hw_argc - 2; i++)
 809                         len += strlen(as->argv[i]) + 1;
 810                 p = m->hw_handler_params = kzalloc(len, GFP_KERNEL);
 811                 if (!p) {
 812                         ti->error = "memory allocation failed";
 813                         ret = -ENOMEM;
 814                         goto fail;
 815                 }
 816                 j = sprintf(p, "%d", hw_argc - 1);
 817                 for (i = 0, p+=j+1; i <= hw_argc - 2; i++, p+=j+1)
 818                         j = sprintf(p, "%s", as->argv[i]);
 819         }
 820         consume(as, hw_argc - 1);
 821
 822         return 0;
 823 fail:
 824         kfree(m->hw_handler_name);
 825         m->hw_handler_name = NULL;
 826         return ret;
 827 }
 828
 829 static int parse_features(struct arg_set *as, struct multipath *m)
 830 {
 831         int r;
 832         unsigned argc;
 833         struct dm_target *ti = m->ti;
 834         const char *param_name;
 835
 836         static struct param _params[] = {
 837                 {0, 3, "invalid number of feature args"},
 838                 {1, 50, "pg_init_retries must be between 1 and 50"},
 839         };
 840
 841         r = read_param(_params, shift(as), &argc, &ti->error);
 842         if (r)
 843                 return -EINVAL;
 844
 845         if (!argc)
 846                 return 0;
 847
 848         do {
 849                 param_name = shift(as);
 850                 argc--;
 851
 852                 if (!strnicmp(param_name, MESG_STR("queue_if_no_path"))) {
 853                         r = queue_if_no_path(m, 1, 0);
 854                         continue;
 855                 }
 856
 857                 if (!strnicmp(param_name, MESG_STR("no_partitions"))) {
 858                         m->features |= FEATURE_NO_PARTITIONS;
 859                         continue;
 860                 }
 861                 if (!strnicmp(param_name, MESG_STR("pg_init_retries")) &&
 862                     (argc >= 1)) {
 863                         r = read_param(_params + 1, shift(as),
 864                                        &m->pg_init_retries, &ti->error);
 865                         argc--;
 866                         continue;
 867                 }
 868
 869                 ti->error = "Unrecognised multipath feature request";
 870                 r = -EINVAL;
 871         } while (argc && !r);
 872
 873         return r;
 874 }
 875
 876 static int multipath_ctr(struct dm_target *ti, unsigned int argc,
 877                          char **argv)
 878 {
 879         /* target parameters */
 880         static struct param _params[] = {
 881                 {0, 1024, "invalid number of priority groups"},
 882                 {0, 1024, "invalid initial priority group number"},
 883         };
 884
 885         int r;
 886         struct multipath *m;
 887         struct arg_set as;
 888         unsigned pg_count = 0;
 889         unsigned next_pg_num;
 890
 891         as.argc = argc;
 892         as.argv = argv;
 893
 894         m = alloc_multipath(ti);
 895         if (!m) {
 896                 ti->error = "can't allocate multipath";
 897                 return -EINVAL;
 898         }
 899
 900         r = parse_features(&as, m);
 901         if (r)
 902                 goto bad;
 903
 904         r = parse_hw_handler(&as, m);
 905         if (r)
 906                 goto bad;
 907
 908         r = read_param(_params, shift(&as), &m->nr_priority_groups, &ti->error);
 909         if (r)
 910                 goto bad;
 911
 912         r = read_param(_params + 1, shift(&as), &next_pg_num, &ti->error);
 913         if (r)
 914                 goto bad;
 915
 916         /* parse the priority groups */
 917         while (as.argc) {
 918                 struct priority_group *pg;
 919
 920                 pg = parse_priority_group(&as, m);
 921                 if (IS_ERR(pg)) {
 922                         r = PTR_ERR(pg);
 923                         goto bad;
 924                 }
 925
 926                 m->nr_valid_paths += pg->nr_pgpaths;
 927                 list_add_tail(&pg->list, &m->priority_groups);
 928                 pg_count++;
 929                 pg->pg_num = pg_count;
 930                 if (!--next_pg_num)
 931                         m->next_pg = pg;
 932         }
 933
 934         if (pg_count != m->nr_priority_groups) {
 935                 ti->error = "priority group count mismatch";
 936                 r = -EINVAL;
 937                 goto bad;
 938         }
 939
 940         ti->num_flush_requests = 1;
 941
 942         return 0;
 943
 944  bad:
 945         free_multipath(m);
 946         return r;
 947 }
 948
 949 static void multipath_wait_for_pg_init_completion(struct multipath *m)
 950 {
 951         DECLARE_WAITQUEUE(wait, current);
 952         unsigned long flags;
 953
 954         add_wait_queue(&m->pg_init_wait, &wait);
 955
 956         while (1) {
 957                 set_current_state(TASK_UNINTERRUPTIBLE);
 958
 959                 spin_lock_irqsave(&m->lock, flags);
 960                 if (!m->pg_init_in_progress) {
 961                         spin_unlock_irqrestore(&m->lock, flags);
 962                         break;
 963                 }
 964                 spin_unlock_irqrestore(&m->lock, flags);
 965
 966                 io_schedule();
 967         }
 968         set_current_state(TASK_RUNNING);
 969
 970         remove_wait_queue(&m->pg_init_wait, &wait);
 971 }
 972
 973 static void flush_multipath_work(struct multipath *m)
 974 {
 975         flush_workqueue(kmpath_handlerd);
 976         multipath_wait_for_pg_init_completion(m);
 977         flush_workqueue(kmultipathd);
 978         flush_scheduled_work();
 979 }
 980
 981 static void multipath_dtr(struct dm_target *ti)
 982 {
 983         struct multipath *m = ti->private;
 984
 985         flush_multipath_work(m);
 986         free_multipath(m);
 987 }
 988
 989 /*
 990  * Map cloned requests
 991  */
 992 static int multipath_map(struct dm_target *ti, struct request *clone,
 993                          union map_info *map_context)
 994 {
 995         int r;
 996         struct dm_mpath_io *mpio;
 997         struct multipath *m = (struct multipath *) ti->private;
 998
 999         mpio = mempool_alloc(m->mpio_pool, GFP_ATOMIC);
1000         if (!mpio)
1001                 /* ENOMEM, requeue */
1002                 return DM_MAPIO_REQUEUE;
1003         memset(mpio, 0, sizeof(*mpio));
1004
1005         map_context->ptr = mpio;
1006         clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
1007         /* Always attach a sense buffer */
1008         if (!clone->sense)
1009                 clone->sense = mpio->sense;
1010         r = map_io(m, clone, mpio, 0);
1011         if (r < 0 || r == DM_MAPIO_REQUEUE)
1012                 mempool_free(mpio, m->mpio_pool);
1013
1014         return r;
1015 }
1016
1017 /*
1018  * Take a path out of use.
1019  */
1020 static int fail_path(struct pgpath *pgpath)
1021 {
1022         unsigned long flags;
1023         struct multipath *m = pgpath->pg->m;
1024
1025         spin_lock_irqsave(&m->lock, flags);
1026
1027         if (!pgpath->is_active)
1028                 goto out;
1029
1030         DMWARN("Failing path %s.", pgpath->path.pdev);
1031
1032         pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
1033         pgpath->is_active = 0;
1034         pgpath->fail_count++;
1035
1036         m->nr_valid_paths--;
1037
1038         if (pgpath == m->current_pgpath)
1039                 m->current_pgpath = NULL;
1040
1041         dm_path_uevent(DM_UEVENT_PATH_FAILED, m->ti,
1042                        pgpath->path.pdev, m->nr_valid_paths);
1043
1044         schedule_work(&m->trigger_event);
1045         queue_work(kmultipathd, &pgpath->deactivate_path);
1046
1047 out:
1048         spin_unlock_irqrestore(&m->lock, flags);
1049
1050         return 0;
1051 }
1052
1053 /*
1054  * Reinstate a previously-failed path
1055  */
1056 static int reinstate_path(struct pgpath *pgpath)
1057 {
1058         int r = 0;
1059         unsigned long flags;
1060         struct multipath *m = pgpath->pg->m;
1061
1062         spin_lock_irqsave(&m->lock, flags);
1063
1064         if (pgpath->is_active)
1065                 goto out;
1066
1067         if (!pgpath->path.dev) {
1068                 DMWARN("Cannot reinstate disabled path %s", pgpath->path.pdev);
1069                 r = -ENODEV;
1070                 goto out;
1071         }
1072
1073         if (!pgpath->pg->ps.type->reinstate_path) {
1074                 DMWARN("Reinstate path not supported by path selector %s",
1075                        pgpath->pg->ps.type->name);
1076                 r = -EINVAL;
1077                 goto out;
1078         }
1079
1080         r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
1081         if (r)
1082                 goto out;
1083
1084         pgpath->is_active = 1;
1085
1086         if (!m->nr_valid_paths++ && m->queue_size) {
1087                 m->current_pgpath = NULL;
1088                 queue_work(kmultipathd, &m->process_queued_ios);
1089         } else if (m->hw_handler_name && (m->current_pg == pgpath->pg)) {
1090                 if (queue_work(kmpath_handlerd, &pgpath->activate_path))
1091                         m->pg_init_in_progress++;
1092         }
1093
1094         dm_path_uevent(DM_UEVENT_PATH_REINSTATED, m->ti,
1095                        pgpath->path.pdev, m->nr_valid_paths);
1096
1097         schedule_work(&m->trigger_event);
1098
1099 out:
1100         spin_unlock_irqrestore(&m->lock, flags);
1101
1102         return r;
1103 }
1104
1105 /*
1106  * Fail or reinstate all paths that match the provided struct dm_dev.
1107  */
1108 static int action_dev(struct multipath *m, struct dm_dev *dev,
1109                       action_fn action)
1110 {
1111         int r = 0;
1112         struct pgpath *pgpath;
1113         struct priority_group *pg;
1114
1115         if (!dev)
1116                 return 0;
1117
1118         list_for_each_entry(pg, &m->priority_groups, list) {
1119                 list_for_each_entry(pgpath, &pg->pgpaths, list) {
1120                         if (pgpath->path.dev == dev)
1121                                 r = action(pgpath);
1122                 }
1123         }
1124
1125         return r;
1126 }
1127
1128 /*
1129  * Temporarily try to avoid having to use the specified PG
1130  */
1131 static void bypass_pg(struct multipath *m, struct priority_group *pg,
1132                       int bypassed)
1133 {
1134         unsigned long flags;
1135
1136         spin_lock_irqsave(&m->lock, flags);
1137
1138         pg->bypassed = bypassed;
1139         m->current_pgpath = NULL;
1140         m->current_pg = NULL;
1141
1142         spin_unlock_irqrestore(&m->lock, flags);
1143
1144         schedule_work(&m->trigger_event);
1145 }
1146
1147 /*
1148  * Switch to using the specified PG from the next I/O that gets mapped
1149  */
1150 static int switch_pg_num(struct multipath *m, const char *pgstr)
1151 {
1152         struct priority_group *pg;
1153         unsigned pgnum;
1154         unsigned long flags;
1155
1156         if (!pgstr || (sscanf(pgstr, "%u", &pgnum) != 1) || !pgnum ||
1157             (pgnum > m->nr_priority_groups)) {
1158                 DMWARN("invalid PG number supplied to switch_pg_num");
1159                 return -EINVAL;
1160         }
1161
1162         spin_lock_irqsave(&m->lock, flags);
1163         list_for_each_entry(pg, &m->priority_groups, list) {
1164                 pg->bypassed = 0;
1165                 if (--pgnum)
1166                         continue;
1167
1168                 m->current_pgpath = NULL;
1169                 m->current_pg = NULL;
1170                 m->next_pg = pg;
1171         }
1172         spin_unlock_irqrestore(&m->lock, flags);
1173
1174         schedule_work(&m->trigger_event);
1175         return 0;
1176 }
1177
1178 /*
1179  * Set/clear bypassed status of a PG.
1180  * PGs are numbered upwards from 1 in the order they were declared.
1181  */
1182 static int bypass_pg_num(struct multipath *m, const char *pgstr, int bypassed)
1183 {
1184         struct priority_group *pg;
1185         unsigned pgnum;
1186
1187         if (!pgstr || (sscanf(pgstr, "%u", &pgnum) != 1) || !pgnum ||
1188             (pgnum > m->nr_priority_groups)) {
1189                 DMWARN("invalid PG number supplied to bypass_pg");
1190                 return -EINVAL;
1191         }
1192
1193         list_for_each_entry(pg, &m->priority_groups, list) {
1194                 if (!--pgnum)
1195                         break;
1196         }
1197
1198         bypass_pg(m, pg, bypassed);
1199         return 0;
1200 }
1201
1202 /*
1203  * Should we retry pg_init immediately?
1204  */
1205 static int pg_init_limit_reached(struct multipath *m, struct pgpath *pgpath)
1206 {
1207         unsigned long flags;
1208         int limit_reached = 0;
1209
1210         spin_lock_irqsave(&m->lock, flags);
1211
1212         if (m->pg_init_count <= m->pg_init_retries)
1213                 m->pg_init_required = 1;
1214         else
1215                 limit_reached = 1;
1216
1217         spin_unlock_irqrestore(&m->lock, flags);
1218
1219         return limit_reached;
1220 }
1221
1222 static void pg_init_done(void *data, int errors)
1223 {
1224         struct pgpath *pgpath = data;
1225         struct priority_group *pg = pgpath->pg;
1226         struct multipath *m = pg->m;
1227         unsigned long flags;
1228
1229         /* device or driver problems */
1230         switch (errors) {
1231         case SCSI_DH_OK:
1232                 break;
1233         case SCSI_DH_NOSYS:
1234                 if (!m->hw_handler_name) {
1235                         errors = 0;
1236                         break;
1237                 }
1238                 DMERR("Count not failover device %s: Handler scsi_dh_%s "
1239                       "was not loaded.", pgpath->path.pdev,
1240                       m->hw_handler_name);
1241                 /*
1242                  * Fail path for now, so we do not ping pong
1243                  */
1244                 fail_path(pgpath);
1245                 break;
1246         case SCSI_DH_DEV_TEMP_BUSY:
1247                 /*
1248                  * Probably doing something like FW upgrade on the
1249                  * controller so try the other pg.
1250                  */
1251                 bypass_pg(m, pg, 1);
1252                 break;
1253         case SCSI_DH_DEV_OFFLINED:
1254                 DMWARN("Device %s offlined.", pgpath->path.pdev);
1255                 errors = 0;
1256                 break;
1257         /* TODO: For SCSI_DH_RETRY we should wait a couple seconds */
1258         case SCSI_DH_RETRY:
1259         case SCSI_DH_IMM_RETRY:
1260         case SCSI_DH_RES_TEMP_UNAVAIL:
1261                 if (pg_init_limit_reached(m, pgpath))
1262                         fail_path(pgpath);
1263                 errors = 0;
1264                 break;
1265         default:
1266                 /*
1267                  * We probably do not want to fail the path for a device
1268                  * error, but this is what the old dm did. In future
1269                  * patches we can do more advanced handling.
1270                  */
1271                 fail_path(pgpath);
1272         }
1273
1274         spin_lock_irqsave(&m->lock, flags);
1275         if (errors) {
1276                 if (pgpath == m->current_pgpath) {
1277                         DMERR("Could not failover device %s, error %d.",
1278                               pgpath->path.pdev, errors);
1279                         m->current_pgpath = NULL;
1280                         m->current_pg = NULL;
1281                 }
1282         } else if (!m->pg_init_required)
1283                 pg->bypassed = 0;
1284
1285         if (--m->pg_init_in_progress)
1286                 /* Activations of other paths are still on going */
1287                 goto out;
1288
1289         if (!m->pg_init_required)
1290                 m->queue_io = 0;
1291
1292         queue_work(kmultipathd, &m->process_queued_ios);
1293
1294         /*
1295          * Wake up any thread waiting to suspend.
1296          */
1297         wake_up(&m->pg_init_wait);
1298
1299 out:
1300         spin_unlock_irqrestore(&m->lock, flags);
1301 }
1302
1303 static void activate_path(struct work_struct *work)
1304 {
1305         struct pgpath *pgpath =
1306                 container_of(work, struct pgpath, activate_path);
1307
1308         if (pgpath->path.dev)
1309                 scsi_dh_activate(bdev_get_queue(pgpath->path.dev->bdev),
1310                                  pg_init_done, pgpath);
1311 }
1312
1313 /*
1314  * Evaluate scsi return code
1315  */
1316 static int eval_scsi_error(int result, char *sense, int sense_len)
1317 {
1318         struct scsi_sense_hdr sshdr;
1319         int r = DM_ENDIO_REQUEUE;
1320
1321         if (host_byte(result) != DID_OK)
1322                 return r;
1323
1324         if (msg_byte(result) != COMMAND_COMPLETE)
1325                 return r;
1326
1327         if (status_byte(result) == RESERVATION_CONFLICT)
1328                 /* Do not retry here, possible data corruption */
1329                 return -EIO;
1330
1331 #if defined(CONFIG_SCSI) || defined(CONFIG_SCSI_MODULE)
1332         if (status_byte(result) == CHECK_CONDITION &&
1333             !scsi_normalize_sense(sense, sense_len, &sshdr)) {
1334
1335                 switch (sshdr.sense_key) {
1336                 case MEDIUM_ERROR:
1337                 case DATA_PROTECT:
1338                 case BLANK_CHECK:
1339                 case COPY_ABORTED:
1340                 case VOLUME_OVERFLOW:
1341                 case MISCOMPARE:
1342                         r = -EIO;
1343                         break;
1344                 }
1345         }
1346 #endif
1347
1348         return r;
1349 }
1350
1351 /*
1352  * end_io handling
1353  */
1354 static int do_end_io(struct multipath *m, struct request *clone,
1355                      int error, struct dm_mpath_io *mpio)
1356 {
1357         /*
1358          * We don't queue any clone request inside the multipath target
1359          * during end I/O handling, since those clone requests don't have
1360          * bio clones.  If we queue them inside the multipath target,
1361          * we need to make bio clones, that requires memory allocation.
1362          * (See drivers/md/dm.c:end_clone_bio() about why the clone requests
1363          *  don't have bio clones.)
1364          * Instead of queueing the clone request here, we queue the original
1365          * request into dm core, which will remake a clone request and
1366          * clone bios for it and resubmit it later.
1367          */
1368         int r = DM_ENDIO_REQUEUE;
1369         unsigned long flags;
1370
1371         if (!error && !clone->errors)
1372                 return 0;       /* I/O complete */
1373
1374         if (error == -EOPNOTSUPP)
1375                 return error;
1376
1377         r = eval_scsi_error(clone->errors, clone->sense, clone->sense_len);
1378         if (r != DM_ENDIO_REQUEUE)
1379                 return r;
1380
1381         if (mpio->pgpath)
1382                 fail_path(mpio->pgpath);
1383
1384         spin_lock_irqsave(&m->lock, flags);
1385         if (!m->nr_valid_paths && !m->queue_if_no_path && !__must_push_back(m))
1386                 r = -EIO;
1387         spin_unlock_irqrestore(&m->lock, flags);
1388
1389         return r;
1390 }
1391
1392 static int multipath_end_io(struct dm_target *ti, struct request *clone,
1393                             int error, union map_info *map_context)
1394 {
1395         struct multipath *m = ti->private;
1396         struct dm_mpath_io *mpio = map_context->ptr;
1397         struct pgpath *pgpath = mpio->pgpath;
1398         struct path_selector *ps;
1399         int r;
1400
1401         r  = do_end_io(m, clone, error, mpio);
1402         if (pgpath) {
1403                 ps = &pgpath->pg->ps;
1404                 if (ps->type->end_io)
1405                         ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes);
1406         }
1407         if (clone->sense == mpio->sense) {
1408                 clone->sense = NULL;
1409                 clone->sense_len = 0;
1410         }
1411         mempool_free(mpio, m->mpio_pool);
1412
1413         return r;
1414 }
1415
1416 /*
1417  * Suspend can't complete until all the I/O is processed so if
1418  * the last path fails we must error any remaining I/O.
1419  * Note that if the freeze_bdev fails while suspending, the
1420  * queue_if_no_path state is lost - userspace should reset it.
1421  */
1422 static void multipath_presuspend(struct dm_target *ti)
1423 {
1424         struct multipath *m = (struct multipath *) ti->private;
1425
1426         queue_if_no_path(m, 0, 1);
1427 }
1428
1429 static void multipath_postsuspend(struct dm_target *ti)
1430 {
1431         struct multipath *m = ti->private;
1432
1433         mutex_lock(&m->work_mutex);
1434         flush_multipath_work(m);
1435         mutex_unlock(&m->work_mutex);
1436 }
1437
1438 /*
1439  * Restore the queue_if_no_path setting.
1440  */
1441 static void multipath_resume(struct dm_target *ti)
1442 {
1443         struct multipath *m = (struct multipath *) ti->private;
1444         unsigned long flags;
1445
1446         spin_lock_irqsave(&m->lock, flags);
1447         m->queue_if_no_path = m->saved_queue_if_no_path;
1448         spin_unlock_irqrestore(&m->lock, flags);
1449 }
1450
1451 /*
1452  * Info output has the following format:
1453  * num_multipath_feature_args [multipath_feature_args]*
1454  * num_handler_status_args [handler_status_args]*
1455  * num_groups init_group_number
1456  *            [A|D|E num_ps_status_args [ps_status_args]*
1457  *             num_paths num_selector_args
1458  *             [path_dev A|F fail_count [selector_args]* ]+ ]+
1459  *
1460  * Table output has the following format (identical to the constructor string):
1461  * num_feature_args [features_args]*
1462  * num_handler_args hw_handler [hw_handler_args]*
1463  * num_groups init_group_number
1464  *     [priority selector-name num_ps_args [ps_args]*
1465  *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1466  */
1467 static int multipath_status(struct dm_target *ti, status_type_t type,
1468                             char *result, unsigned int maxlen)
1469 {
1470         int sz = 0;
1471         unsigned long flags;
1472         struct multipath *m = (struct multipath *) ti->private;
1473         struct priority_group *pg;
1474         struct pgpath *p;
1475         unsigned pg_num;
1476         char state;
1477
1478         spin_lock_irqsave(&m->lock, flags);
1479
1480         /* Features */
1481         if (type == STATUSTYPE_INFO)
1482                 DMEMIT("2 %u %u ", m->queue_size, m->pg_init_count);
1483         else {
1484                 DMEMIT("%u ", m->queue_if_no_path +
1485                               (m->pg_init_retries > 0) * 2 +
1486                               (m->features & FEATURE_NO_PARTITIONS));
1487                 if (m->queue_if_no_path)
1488                         DMEMIT("queue_if_no_path ");
1489                 if (m->pg_init_retries)
1490                         DMEMIT("pg_init_retries %u ", m->pg_init_retries);
1491                 if (m->features & FEATURE_NO_PARTITIONS)
1492                         DMEMIT("no_partitions ");
1493         }
1494
1495         if (!m->hw_handler_name || type == STATUSTYPE_INFO)
1496                 DMEMIT("0 ");
1497         else
1498                 DMEMIT("1 %s ", m->hw_handler_name);
1499
1500         DMEMIT("%u ", m->nr_priority_groups);
1501
1502         if (m->next_pg)
1503                 pg_num = m->next_pg->pg_num;
1504         else if (m->current_pg)
1505                 pg_num = m->current_pg->pg_num;
1506         else
1507                         pg_num = 1;
1508
1509         DMEMIT("%u ", pg_num);
1510
1511         switch (type) {
1512         case STATUSTYPE_INFO:
1513                 list_for_each_entry(pg, &m->priority_groups, list) {
1514                         if (pg->bypassed)
1515                                 state = 'D';    /* Disabled */
1516                         else if (pg == m->current_pg)
1517                                 state = 'A';    /* Currently Active */
1518                         else
1519                                 state = 'E';    /* Enabled */
1520
1521                         DMEMIT("%c ", state);
1522
1523                         if (pg->ps.type->status)
1524                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1525                                                           result + sz,
1526                                                           maxlen - sz);
1527                         else
1528                                 DMEMIT("0 ");
1529
1530                         DMEMIT("%u %u ", pg->nr_pgpaths,
1531                                pg->ps.type->info_args);
1532
1533                         list_for_each_entry(p, &pg->pgpaths, list) {
1534                                 DMEMIT("%s %s %u ", p->path.pdev,
1535                                        p->is_active ? "A" : "F",
1536                                        p->fail_count);
1537                                 if (pg->ps.type->status)
1538                                         sz += pg->ps.type->status(&pg->ps,
1539                                               &p->path, type, result + sz,
1540                                               maxlen - sz);
1541                         }
1542                 }
1543                 break;
1544
1545         case STATUSTYPE_TABLE:
1546                 list_for_each_entry(pg, &m->priority_groups, list) {
1547                         DMEMIT("%s ", pg->ps.type->name);
1548
1549                         if (pg->ps.type->status)
1550                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1551                                                           result + sz,
1552                                                           maxlen - sz);
1553                         else
1554                                 DMEMIT("0 ");
1555
1556                         DMEMIT("%u %u ", pg->nr_pgpaths,
1557                                pg->ps.type->table_args);
1558
1559                         list_for_each_entry(p, &pg->pgpaths, list) {
1560                                 DMEMIT("%s ", p->path.pdev);
1561                                 if (pg->ps.type->status)
1562                                         sz += pg->ps.type->status(&pg->ps,
1563                                               &p->path, type, result + sz,
1564                                               maxlen - sz);
1565                         }
1566                 }
1567                 break;
1568         }
1569
1570         spin_unlock_irqrestore(&m->lock, flags);
1571
1572         return 0;
1573 }
1574
1575 static int multipath_message(struct dm_target *ti, unsigned argc, char **argv)
1576 {
1577         int r = -EINVAL;
1578         struct dm_dev *dev;
1579         struct multipath *m = (struct multipath *) ti->private;
1580         action_fn action;
1581
1582         mutex_lock(&m->work_mutex);
1583
1584         if (dm_suspended(ti)) {
1585                 r = -EBUSY;
1586                 goto out;
1587         }
1588
1589         if (argc == 1) {
1590                 if (!strnicmp(argv[0], MESG_STR("queue_if_no_path"))) {
1591                         r = queue_if_no_path(m, 1, 0);
1592                         goto out;
1593                 } else if (!strnicmp(argv[0], MESG_STR("fail_if_no_path"))) {
1594                         r = queue_if_no_path(m, 0, 0);
1595                         goto out;
1596                 }
1597         }
1598
1599         if (argc != 2) {
1600                 DMWARN("Unrecognised multipath message received.");
1601                 goto out;
1602         }
1603
1604         if (!strnicmp(argv[0], MESG_STR("disable_group"))) {
1605                 r = bypass_pg_num(m, argv[1], 1);
1606                 goto out;
1607         } else if (!strnicmp(argv[0], MESG_STR("enable_group"))) {
1608                 r = bypass_pg_num(m, argv[1], 0);
1609                 goto out;
1610         } else if (!strnicmp(argv[0], MESG_STR("switch_group"))) {
1611                 r = switch_pg_num(m, argv[1]);
1612                 goto out;
1613         } else if (!strnicmp(argv[0], MESG_STR("reinstate_path")))
1614                 action = reinstate_path;
1615         else if (!strnicmp(argv[0], MESG_STR("fail_path")))
1616                 action = fail_path;
1617         else {
1618                 DMWARN("Unrecognised multipath message received.");
1619                 goto out;
1620         }
1621
1622         r = dm_get_device(ti, argv[1], dm_table_get_mode(ti->table), &dev);
1623         if (r) {
1624                 DMWARN("message: error getting device %s",
1625                        argv[1]);
1626                 goto out;
1627         }
1628
1629         r = action_dev(m, dev, action);
1630
1631         dm_put_device(ti, dev);
1632
1633 out:
1634         mutex_unlock(&m->work_mutex);
1635         return r;
1636 }
1637
1638 static int multipath_ioctl(struct dm_target *ti, unsigned int cmd,
1639                            unsigned long arg)
1640 {
1641         struct multipath *m = (struct multipath *) ti->private;
1642         struct block_device *bdev = NULL;
1643         fmode_t mode = 0;
1644         unsigned long flags;
1645         int r = 0;
1646
1647         spin_lock_irqsave(&m->lock, flags);
1648
1649         if (!m->current_pgpath)
1650                 __choose_pgpath(m, 0);
1651
1652         if (m->current_pgpath && m->current_pgpath->path.dev) {
1653                 bdev = m->current_pgpath->path.dev->bdev;
1654                 mode = m->current_pgpath->path.dev->mode;
1655         }
1656
1657         if (m->queue_io)
1658                 r = -EAGAIN;
1659         else if (!bdev)
1660                 r = -EIO;
1661
1662         spin_unlock_irqrestore(&m->lock, flags);
1663
1664         return r ? : __blkdev_driver_ioctl(bdev, mode, cmd, arg);
1665 }
1666
1667 static int multipath_iterate_devices(struct dm_target *ti,
1668                                      iterate_devices_callout_fn fn, void *data)
1669 {
1670         struct multipath *m = ti->private;
1671         struct priority_group *pg;
1672         struct pgpath *p;
1673         int ret = 0;
1674
1675         list_for_each_entry(pg, &m->priority_groups, list) {
1676                 list_for_each_entry(p, &pg->pgpaths, list) {
1677                         ret = fn(ti, p->path.dev, ti->begin, ti->len, data);
1678                         if (ret)
1679                                 goto out;
1680                 }
1681         }
1682
1683 out:
1684         return ret;
1685 }
1686
1687 static int __pgpath_busy(struct pgpath *pgpath)
1688 {
1689         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1690
1691         return dm_underlying_device_busy(q);
1692 }
1693
1694 /*
1695  * We return "busy", only when we can map I/Os but underlying devices
1696  * are busy (so even if we map I/Os now, the I/Os will wait on
1697  * the underlying queue).
1698  * In other words, if we want to kill I/Os or queue them inside us
1699  * due to map unavailability, we don't return "busy".  Otherwise,
1700  * dm core won't give us the I/Os and we can't do what we want.
1701  */
1702 static int multipath_busy(struct dm_target *ti)
1703 {
1704         int busy = 0, has_active = 0;
1705         struct multipath *m = ti->private;
1706         struct priority_group *pg;
1707         struct pgpath *pgpath;
1708         unsigned long flags;
1709
1710         spin_lock_irqsave(&m->lock, flags);
1711
1712         /* Guess which priority_group will be used at next mapping time */
1713         if (unlikely(!m->current_pgpath && m->next_pg))
1714                 pg = m->next_pg;
1715         else if (likely(m->current_pg))
1716                 pg = m->current_pg;
1717         else
1718                 /*
1719                  * We don't know which pg will be used at next mapping time.
1720                  * We don't call __choose_pgpath() here to avoid to trigger
1721                  * pg_init just by busy checking.
1722                  * So we don't know whether underlying devices we will be using
1723                  * at next mapping time are busy or not. Just try mapping.
1724                  */
1725                 goto out;
1726
1727         /*
1728          * If there is one non-busy active path at least, the path selector
1729          * will be able to select it. So we consider such a pg as not busy.
1730          */
1731         busy = 1;
1732         list_for_each_entry(pgpath, &pg->pgpaths, list)
1733                 if (pgpath->is_active) {
1734                         has_active = 1;
1735
1736                         if (!__pgpath_busy(pgpath)) {
1737                                 busy = 0;
1738                                 break;
1739                         }
1740                 }
1741
1742         if (!has_active)
1743                 /*
1744                  * No active path in this pg, so this pg won't be used and
1745                  * the current_pg will be changed at next mapping time.
1746                  * We need to try mapping to determine it.
1747                  */
1748                 busy = 0;
1749
1750 out:
1751         spin_unlock_irqrestore(&m->lock, flags);
1752
1753         return busy;
1754 }
1755
1756 /*-----------------------------------------------------------------
1757  * Module setup
1758  *---------------------------------------------------------------*/
1759 static struct target_type multipath_target = {
1760         .name = "multipath",
1761         .version = {1, 1, 1},
1762         .module = THIS_MODULE,
1763         .ctr = multipath_ctr,
1764         .dtr = multipath_dtr,
1765         .map_rq = multipath_map,
1766         .rq_end_io = multipath_end_io,
1767         .presuspend = multipath_presuspend,
1768         .postsuspend = multipath_postsuspend,
1769         .resume = multipath_resume,
1770         .status = multipath_status,
1771         .message = multipath_message,
1772         .ioctl  = multipath_ioctl,
1773         .iterate_devices = multipath_iterate_devices,
1774         .busy = multipath_busy,
1775 };
1776
1777 static int __init dm_multipath_init(void)
1778 {
1779         int r;
1780
1781         /* allocate a slab for the dm_ios */
1782         _mpio_cache = KMEM_CACHE(dm_mpath_io, 0);
1783         if (!_mpio_cache)
1784                 return -ENOMEM;
1785
1786         r = dm_register_target(&multipath_target);
1787         if (r < 0) {
1788                 DMERR("register failed %d", r);
1789                 kmem_cache_destroy(_mpio_cache);
1790                 return -EINVAL;
1791         }
1792
1793         kmultipathd = create_workqueue("kmpathd");
1794         if (!kmultipathd) {
1795                 DMERR("failed to create workqueue kmpathd");
1796                 dm_unregister_target(&multipath_target);
1797                 kmem_cache_destroy(_mpio_cache);
1798                 return -ENOMEM;
1799         }
1800
1801         /*
1802          * A separate workqueue is used to handle the device handlers
1803          * to avoid overloading existing workqueue. Overloading the
1804          * old workqueue would also create a bottleneck in the
1805          * path of the storage hardware device activation.
1806          */
1807         kmpath_handlerd = create_singlethread_workqueue("kmpath_handlerd");
1808         if (!kmpath_handlerd) {
1809                 DMERR("failed to create workqueue kmpath_handlerd");
1810                 destroy_workqueue(kmultipathd);
1811                 dm_unregister_target(&multipath_target);
1812                 kmem_cache_destroy(_mpio_cache);
1813                 return -ENOMEM;
1814         }
1815
1816         DMINFO("version %u.%u.%u loaded",
1817                multipath_target.version[0], multipath_target.version[1],
1818                multipath_target.version[2]);
1819
1820         return r;
1821 }
1822
1823 static void __exit dm_multipath_exit(void)
1824 {
1825         destroy_workqueue(kmpath_handlerd);
1826         destroy_workqueue(kmultipathd);
1827
1828         dm_unregister_target(&multipath_target);
1829         kmem_cache_destroy(_mpio_cache);
1830 }
1831
1832 module_init(dm_multipath_init);
1833 module_exit(dm_multipath_exit);
1834
1835 MODULE_DESCRIPTION(DM_NAME " multipath target");
1836 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
1837 MODULE_LICENSE("GPL");